Dragonslayer (Twilight #1)

Kill the dragon, marry the princess, and rule the kingdom. It's a fantasy come true... if you're straight.

Adam is a chemistry student and martial artist, active in his local chapter of the Society for Creative Anachronism. But none of that prepares him to be the savior of a faraway land locked in perpetual dusk.

In a world of shape-shifters, necromancy, and religious politics, Adam is fated to slay the golden dragon, Khalivibra, and defeat its mind-controlling sorcery to help Princess Esmeralda of Aergon retake her city. Tradition dictates he'll rule by her side--but Adam is much more interested in Duin, a warrior who changes to beast form in the light of the sun... or fire.

Adam hopes he and Duin might end up together when their ordeal ends. But first, the reluctant hero, the spell-casting heir to the throne, the beast-shifting object of Adam's desire, a six-legged cave lizard, and any allies they can gather must do the impossible... and live to celebrate their victory.